Automatic pilots



De 17, 1957 `.1. w. ANDERsoN 2,816,722

AUTOMATIC PILOTS Filed Jan. 25, 1950 2 Sheets-Sheet l Dec. 17, 1957 J. w. ANDERSON AUTOMATIC PILOTS 2 Sheets-Sheet 2 Filed Jan. 23. 1950 IN V EN TOR.

ATTORNEY I ovm .vnu

JOHN W. ANDERSON o: www- .I U .9.. 5. 0 LIFmw. moho: mt

6 Sinai a nos@ wEzoFzEon. o

United States Patent C AUroMATicfPlL-o'rs lohn.W. Anderson,fEdina,.Mnn., assignor to Minneapoli's'Honeywell Regulator` ,Company, Minneapolis, "`Minn., acorporation of Delaware \-Application-Ianuary, 1950, SerialNo. 140,035

"22 Claims. (Cl. 244-177) ."fFI'his-inventionpertains tozsteeringmechanismsor auto- Afmatic pilots .for' dirigible;` .craft 1'such as laircraft, water v craft, andthe like. The nventionfor purposegof illusrtratiomhas been embodieda-in aptype of automatic pilot wherein. automatic-.directional control: is obtained-from affdirectional: gyroscoperwhich is.slaved Itof a'magnetic compass by suitable precessing means.

z-.Itis .an objectof' this. invention ;to. Yprovide novel |means operativesonthat .during the setting- -up of-isaid '.slavedrelationship betweenfthe compass andgyroscope a e ih'igher .precession rate -for :said gyroscope -is available than is available after the gyroscope and vcompass..have been aligned.

It is a further` object :'of zthis' invention .to establish 'an `interval during -which :the high precessionirate-:may

-`. 1-'beexertedr tto fetfect alignment :between .the ;compass and gyrosoope-prior to :the fimpositionfof-said automatic .di-

rectional control of s'aid .craft by lsaidgyroscope.

It is aturther object "of this invention `to .include a control .signal pick-off `"effective bupon relativeidisplace- =ment of Vthe craft and gyroscope for governing=said directional` control with -further vmeans controlled z bye .said

pick-'ott for removing the 'etectf of ysaid l'relative displace- -ment prior to the imposition of automatic .directional-control.

It is a further object ofthisinvention to vprovide a selectivemanuallyoperable coursechanger-feiectivel to operate through said gyroscope. The course changeradditionally-includes -means to prevent the imposition of -automatic directional control initially untilsaid manual coursechanger is in a normal position.

lt is a further'objectof this'invention to provide an improved arrangementl wherein automatic control'of said aircraft may be imposeddespiteanyno'n-level=attitude of -said -craft with said non-level 'attitude beinghthereafter maintained In this arrangement, selectivetdevices ymay -be subsequently operated to return the craft to a preset vattitude dilering fromv said non-level attitude. While the craft-proceeds to suchvpreset attitude, the gyroscope picky'ot is momentarily associated withthe means for removing any-effect therein due tof relative displacement of said lcraft and gyroscope. Additionally the manually operable Vcourse changer is-renderedinetective in the operations to return -the'icraft to a vpreset attitude.

-These-andvfurther/objects` of-thednvention will; be

Lmorefully' brought out -on-^reference tothe accompanying description andedrawing-disclosing onelembodiment of `the invention.

"'=The invention by way of illustration is--shown1inthe accompanying drawingwherein:

Figure 1 is a schematic arra-ngement of -theautomatic pilot, and

"Figure 2 is a schematic diagram of certainspecic portions ofthe automatic pilot the-details whereofbeing vintimately, associated with the invention.

-Refer'ring-'tolPigure 1, amagnetic compassi'which is of example as ainiagnetic needle 10. 'Themeedle 10 2,816,722 ce Patented Dec. 17, 1957 2 Athrough `a spindlell positions a single. phase ywinding j'1 2of a.synchro transmitter 13. rlhe single phase windivng 12 `is energized fromra suitable source of alternating .c xnjrent'. The transmitter 13 includesa three winding statorv 14 which is relatively fixed to the crz 1ft.V The windi ng 14 has triple voltagesinducedin its win d i ngs which voltages correspond to the relative positions of the winding 12 with respect to the ,winding 14. T he windings v of s ta 1tor 14 are connected to the correspondingpolyphase-.windings of a stator 16 ofk a signal transformer 17. `A;singlephase.winding 418 of ,signaltransformer 17 is carried-oma vertical spindle y19. The single phase winding ll8voftransformer17.is connected toa preces'sion mot or 1amplifier 20.

- 'lheprecession-motor,amplifier 20 is of the.well known A. C. =disrimi nator type. The amplier 20 is connected to the suitable source of lalternating current. The amplitier 20 inclu des relays 21, 22, Figure 2, whichare alternativelyoperated depending upon the phase relationship between-thevoltage across theleads 24, 25 connected yto -the alternating. current source and that across signal iny. put leads-246,A 27` connected to. the. phase winding 18 of transformer 17. A suitable type ofamplier ishdisclOSd ..in ap a t en t tow. H Gilleet al.No. 2,425,734.

-: Tl 1e amplifier 20 controlsthe `operationofa directional gyroscope -precession motor, 28. j The lp recessilon motor .28

(asshownin ligure 2) maybe an induction motorofthe -splitf phase capacitor.A type having a rotor29 and. ,tield .windings..:81f89 A- emaux-511.94%@ 0f 91.1- .O ach .ninding-atand; is. smeared. Weigand. 0f as irl-,the middle wire in Figure 1 has a common return. The rop- .,positendof winding 81 isconnected,.to..one,contact `.of.single -pole single throwV doublemake ,relay '21 in nected to onecontact of single polesingle throwdouble make relay- 22 in amplifier 20. A condenser 91 is 'connected across the endsof winding 81, 89 adjacent themelay contacts. The rotor 29 is inductively associatedwith Vwindings 81 and 89 and the direction of Vthe induced 33 is rotatable about a vertical-axis 34. Spindle 119 of -vcarried on the trunnions 32 of casing 31.

the signal transformer 17 is aligned with the, gimbal .axis

34 and is supported from the vertical ring 33 .of the vgyroscope 30. The rotor 29 of precession motor 28 may be The stator windings 81, 89 of the precession motor 28.may.be.sup ported by the .vertical gimbal ring 33 and.the.torque tending -to rotate the rotor 29 .and thus the trunnion 32 -causes the gyroscope to precess about the axis 34 thereby .-carryingwith it the single phase winding 18 of transformer 17.

Automatic directional controlwstems from andir'ectional gyro aileron pick-off 36 and a directional gyrorudder pickott 37 which separately forni part of a= twochan'nel automatic pilot for controlling the ailerons and rudder.

Directional gyro aileron pick-off 36 Aof the aileron channel is a component of a balanceable network which additonally includes rebalancing potentiometer 45, a .trim

Y or centering potentiometer 55, and a variableimpedance network70. The balanceable network controls an aileron yservo amplifier 92.

A insulatedsrelation. -.therefrom.

Pickotf or potentiometerl 36 includes a circularsegmental resistor. 38which is carried by agear; 40, but in The gear. ;40 isl .freely rotatable about the axis of a spindle which is in line with the axis 34 of gimbal 33. The pick-off 36 includes a slider 39 which contacts the resistor 38 and the slider 39 is mounted on the spindle 35 which in turn is supported by the vertical gimbal ring 33. The resistor 38 is connected across the ends of a secondary winding 41 of a transformer 42. A center tap of secondary winding 41 is connected to ground. The transformer 42 includes a primary winding 43 which is connected to the source of alternating current.

The rebalancing network 45 consists of a rebalancing potentiometer 46 having a slider 47 and a resistor 48 which is connected across the ends of a secondary wind ing 49 of a transformer 50. The transformer 50 has a primary Winding 51 connected to the alternating current source. The slider 47 is operatively driven from a shaft 53 extending from an aileron servomotor 96 to be described. A lead wire 54 extends from the slider 39 of the directional gyro aileron potentiometer to the slider 47 of the rebalancing potentiometer.

The trim or centering network 55 includes a centering potentiometer 57 having a slider 58 and a resistor 59 which is connected across the ends of a secondary winding 60 of a transformer 61 (Figure l). A lead wire 66 extends from a center tap of secondary winding 49 to a center tap of resistor 59. The slider 58 is operatively connected to a shaft 67 extending from a centering motor 68. The centering motor 68 like centering motor 122, to be referred to may be of the direct current armature permanent magnet field type. The armature brushes of both motors 68 and 122 are shunted by a center tapped resistor 69, Figure 2, whose center tap is connected to ground. The resistor 69 provides for reverse rotation of motor 68.

The impedance network 70 consists of an automatic recovery potentiometer 73, a vertical gyro roll axis potentiometer 77, and a transformer 79. Potentiometer 73 consists of a slider 74 and a resistor 75 which is connected across the ends of a secondary winding of transformer 79. The slider 74 is manually adjustable from a control knob 72. A lead 82 extends from the slider 58 of a centering potentiometer 57 to the slider 74 of the auto recovery potentiometer 73. Potentiometer 76 consists of a slider 77 and a resistor 78 which is connected across a secondary winding 80 in parallel with resistor 75. Transformer 79 includes a primary Winding 51 identical with the primary winding 51 of the rebalancing network 45. This arrangement is provided since a single primary winding may have several secondary windings. The slider 77 is operated by a vertical gyroscope 83.

The vertical gyroscope 83 may be of the type well known in the art having a casing 84 within which is mounted an electrically motor driven rotor (not shown) for rotation about a vertical axis. The casing 84 is carried in an outer gimbal ring 86 upon trunnions 85, 85. The gimbal ring 86 is in turn being carried by trunnions 88, 88 in pedestal bearings 87, 87. The axis of trunnions 88 is in a horizontal plane and at right angles to the axis of trunnions 85. The gyroscope 83 is so arranged in the craft that upon tilt of the craft about the roll axis slider 77 is moved with respect to resistor 78 in a direction and in proportion to the magnitude of a displacement of the craft about its roll axis.

A lead wire 90 extends from slider 77 to amplifier 92 where it is connected to a control electrode therein. A lead wire 94 extending from another control electrode of amplifier 92 is connected to ground and is therefore common with the grounded center tap of secondary winding 41 of transformer 42. It is apparent therefore that a complete control circuit has now been traced for the amplifier 92. The amplifier 92 has power leads connected to the alternating current source.

The amplifier 92 is of the A. C. discriminator typeand 4 may be similar to that shown in Patent 2.425.734 dated August 19, 1947.

An aileron servomotor 96 drives through its operating shaft 53 a cable drum 98 from which extend cables 100. The cables 100 are connected to the cables extending from the manually operable control column (not shown) of the aircraft. The aileron servomotor 96 may be of the type disclosed in the aforesaid Patent 2,425,734. The amplifier 92 reversibly controls the aileron servomotor 96 or the centering motor 68 alternatively depending upon the operation of the aileron engage relay 97 in a manner more fully to be described. In order to illustrate this4 alternative operation leads 102, 103 extending from the centering motor to the aileron engage relay 97 have been. illustrated in broken line.

The directional gyro rudder pick-off 37 of the rudderchannel forms part of a balanceable circuit which addi-- tionally includes rudder servo rebalancing potentiometer 104, a rudder trim potentiometer 118,.and a variable: impedance network 125. The pick-off or potentiometer' 37 includes a slider 107 and a resistor 106. The resistoris cam'ed by a gear 108 in insulated relation therefrom.. The gear 108 is freely rotatable about the axis of spindle: 34. The slider 107 of potentiometer 37 is carried by the spindle 35 which is axed to gimbal ring 33 of the direc-- tional gyro 30. The ends of the resistor 106 are con nected to the corresponding ends of a secondary winding: 109 of transformer 42. The secondary winding 109 has a. grounded center tap.

The rebalancing network 104 includes a rebalancing potentiometer 113 having a resistor 111 and a slider 110. The resistor 111 is connected across the ends of a secondary winding 114 of a transformer 112 having a primary winding 51. The slider is carried by a servomotor shaft 115. A lead wire 116 extends from the slider 107 of the directional gyro rudder potentiometer 37 to the slider 110 of the rebalancing potentiometer 113.

The rudder trim potentiometer 118 consists of a slider 120 and a resistor 119 which resistor is connected across the ends of a secondary winding 63, Figure 2, of a transf former 61. The slider 120 is carried by a shaft 121 operatively driven from a centering motor 122 similarto :the aileron centering motor 68. A lead wire 123 extends from a center tap of secondary winding 114 to a center tap of resistor 119.

The variable impedance network 125 includes an automatic recovery potentiometer 126 consisting of a resistor 127 and a slider 128; a vertical gyro rudder potentiometer 129 consisting of a slider 131 and a resistor 130; and a transformer 132 having a primary winding 51 and a secondary winding 133. The resistors 127 and 130 are connected in parallel across the ends of secondary winding 133. Slider 128 of the automatic recovery potentiom eter 126 is manually adjustable by a control knob 134. A lead 135 extends from the slider 120 of the trim potentiometer to the slider 128. Slider 131 is driven by an operative connection 136 carried by trunnion 85 of the vertical gyro 83. The slider 131 moves with respect to resistor 130 upon movement of the craft about the roll axis. A lead wire 137 extends from slider 131 to one control element in rudder servomotor amplifier 140. A lead wire 162 extends from another control element in amplifier 140 to ground and is therefore common to the grounded center tap of secondary winding 109. Control signals are applied between the lead wires 137 and 162 to control the operation of amplier 140. The amplifier 140 is also connected to the source of alternating current and is thus similar to the alieron amplifier 92.

A rudder servomotor 141 through its shaft 115 drives a cable drum 142. Cables 143 extend from the cable drum 142 and are secured to the main operating cables of the rudder (not shown). The rudder amplifier 140 reversibly controls rudder servomotor 141 or alternatively controls centering motor 122 througha rudder engage relay 144. This alternative control is represented by the broken ,lines 145, 146 representinglead wires extending from the rudder engage relay 144 to the centering motor 122.

Altlflrn control or course changerJ-ISO is provided to make selective changes in headingY ofthe craft. The course changer-150 includes amanually-operable-knob i151 which through itsshaft 152 operates a slider 153- of a potentiometer154. A resistor 155'of-potentiometer-154 is connected across the ends of secondary winding62 of transformer '6P-(Figure 2). A lead wire156 extends from a-center tap-of 4resistor155 to ground. An output lead lwire;1"57-fron; 1 the course change potentiometer 154 extends through Ythe rudder engage relay 144 to theinput `circuit-*of ansteering motor amplifier 160. Included in this-signalinput circuit ofampliler-160 is avelocitygenf erator'-174 to -be-described. The portion of the signal inputfcontrolscircuit of amplifier 160 mentioned above is-connected-'to'one control electrode of amplifier 160. Another control'electrode of amplilier 160 is connected by a lead wire 166 to ground and thence to the grounded lead'f-156 of potentiometer 154. .The amplier 160 is connected to the valternating current power source-through -le`adwires 164, `165.

"-i-The `a1npliter1160 controls the rotation of asteering motor "167.1 The steering motor may be a-single phase induction motor Aof the capacitor type having ono phase v`"-z-winding'connected in series with a condenser 179 tothe f f'alternating current power source 4through leads--169and "1-70.'Th e other phase winding is connected by leadgwires l=1 7-1an d 172 to the output of amplifier 160. The direction Lof rotation of the steering motor' 167 thusdependsfupon -thephase'rela tionship between the voltageacross -the power leadfwires` 164, 165 of amplifier 160 and that across`the v'vfarnpliter signal input terminal connections. The amplifier- Lf-steer-ing motor-combination may be similar to-that in -^-'-applica tion Serial No. 22,841, tiled April 23,1948.

The steering motor 167 through its shaft 162 `drives a-Velocity generator 174. This velocity generatorl con- Asists of a primary winding 175, a secondary winding v176, and -a rotor 177. For purpose of illustration the windings f -'175 and176 have been rotated through 90 from aplane perpendicular to the plane of the drawing; 4additionally -winding 175 has been rotated circumferentially 90 from its normal position about the periphery of rotor/177.V -The primary winding 175 is connected to the alternating cur- -rent source and the secondary winding 176 is inductively related to the primary winding 175 upon rotation of the rotor 177.

The steering motor 167 through its shaft 162 also rotates the gears 181 and 182 which are the driving gears for gears and 108 that support the potentiometer resistor 38 and 106, respectively, to provide changes in heading of the-craft in a manner more fully to be described.

- An aircraft provided with an automatic pilot of the type embodying this invention may have its control sur- -faces -directly manually operated from the conventional v-control column and rudder bar; may have its control surfaces automatically controlled for the purpose of stabilized flight; or may have its control surfaces manually controlled through the automatic pilot to obtain changes in heading of the craft. Figure 2 shows in detail the opera tive relationship between the components of the automatic pilot in accordance with the three various operations to be obtained. An automatic pilot which includes electrically driven gyroscopes and electrical types of pickloff Idevices must have these components connected to a -source of electrical energy. In the present embodiment, thisconnection is provided by a main automatic pilot switch-184. Switch 184 is of the two pole single throw single make type having poles 185 and 186 operated together by a common actuator 187. Poles'185 and 186 of switch 184 control the D. C. and A. C. sections of the automatic pilot. While the A. C. section consistingv of the yarious potentiometer transformers, gyroscope. rotors, and .amplifiers .are .directly fed from-,the alternating current 75 A 4variableresistor.285. is connected across pole 205 and ground.

.terminator..circint.iarontrcllefl by a rotor speed-.Islay f, -190... `Relay, 190` isof .th e,. .t w o pole. doublethrow single make type` .flherelay190.,.ccnsists;of au opcratingfcoil 191Ywhih .through itsnlunger 192. .serves asA an .actuating meansior .the` two ,pole s;193 194. lole"193 operates betweenanout.co ntact 119.5.. and an in contact .196.' kvI ole 19.4 operatesbetween out contact, 197 and'n inVA contact-.198.

...Reve .'ng tol-the, procession motor .23., it is .energized from a transforme1.. 199..t1`he precessionrnotor rtransformer 199 consistsof a primarvwinding 200 and a secondarwwindnazl. .Oneendjof secondary winding ....201.. iS. .cpnnectedthroughampliler 2 0 to the precession 15 .connected into. the.precession motor4 circuitthrough a .motor 28. 'Ihe otherl end o f .se condary winding 201 is singlerole...doublemthrovt...single..make type hai/.ina an actuating .coil i203 Iyvhich. through .a plunger. 204. Operates the pole 205 betweenout contact 206 and in contact'. 207.

Atime delay, deyice.. 209l is .associated .with .'relay. coil 191 .to provide 4initial.,:rapid .alignment of the gyroscope .with the. .compass .prior.to...the time .when the automatic -..p1o,t. ,may be associated with the control surfaces ofA the craft.,.,`.'1 he ,timedqlaydeviceconsists of asingle Apole .ingle...throwsi.nsl make. switch .having a pole. 2.10..and

an irl.,52.91.1tact..211.1 hepolclill is of bimetal construc- 30.

tiQnian'd is. heated. frontaal element 212A adjacent thereto- ,'I11s.i.1`111'=delay` switch'209.. also. controls.. .the .effective- ...ness of a main autopilot engage.S.lll/.itch. 213.i This main vernaageswitchisiof a ,singlepcle single.. throw-normally opcmtemnorary.closedtypeandsmanuallyoperable. 35

AssQsiatedWiththamain engage. switch `213 is .anlan engage relay 216 .which is of the doublepole s ingle,throw single make type. The relay 216 consists of anoperating coil217 whichlhrough its plunger.218A operates the poles 219 and ,220 which, are associated respectively with in contacts,221 and 222. j` AThe contat 221 -is designated the rudder engage relay. ene rgizing Contact and the Contact 222 is designatedthe A aileron .engage relay Aenergizing contact.

Associated with theicontact221 is a rudder engage relay 144. The rudder engagerelay 144 isof. the vepole double throw single make type having an operating coil .224 which through a plungerl225 voperates the poles or Contact arms 226,227, 228, 229,V and 230. Arm,`226 operates between out contact'231 and in contact 232; arm .227 operates between out contact 233 and in ,Contact 234; arm 228 operates between out contact 235 and in contact 236; arm .229 operatesbetween out-.contact 237 .and in contact 238; arm'230 operates between out .con-

. tact 239 and in contact 240. vThe relayarms are.4 biased toward the out position by spring means (notshown).

While the main engage relay 216 is controlled by the main engage switch 219 it is alternatively controlled through an automatic recovery switch.241 and an automatic recovery relay 246. The switch 241 is of the single pole single throw single make normally open type." The switch 241 has a pole or contact arm 242 which is associated with a dash pot spring arrangement 244 through a dash pot plunger 243. When the switch 241 is closed and released the dash pot through its springV moves the pole 242 to open position a short time -after it is adjusted to the closed position theopening timebeing in a nature of approximately seven seconds. Suchdash pot devices are well known in the art and the period required. to open the switch depends merely upon the properselection of the dash pot and spring arrangement 244.

The relay 246 is of the three -pole .dou ble throw'single make type. Relay 246 includes anvoperating1coiln247 which through its plunger,- 248 operates the; pole ongrelay arms-249, .2501and 251. .A rm. f 251,c oacts ,withgan in contact 252; arm 249 coacts with an out contact1253and "255 and an in contact 256.

' deenergization of a primary winding 64 of transformer 61 which supplies the centering and turn potentiometer secondary windings;

During the operation of the aircraft when the automatic pilot is not b'eing utilized such as when the control surfaces are being manually operated directly, the craft may undergo a change in heading' which would result in a Arelative rotation ordisplacement of the aircraft with respect to the directional gyroscope. This would result in a relative displacement 'of the gyro stabilized slider 107 of potentiometer 37 with respect to its i'esistor 106 normally fixed with respect to the craft but rotatable with respect thereto by means to be described. Should it be desired while such relative displacement of gyroscope and craft exists to effect automatic pilot control of the craft it is clear that a residual signal will have been generated which will cause a lurch of the craft upon the imposition of such automatic pilot control. For this purpose, it is desired to maintain the potentiometer 37 in a no signal position while the automatic pilot is not utilized and to this end any voltage generated at pick-off or potentiometer 37 is applied to a primary winding 267, Figure 2, of an isolating transformer 266. The voltage induced in the secondary winding 268 of transformer 266 is subsequently utilized in a manner to be described to drive the pick-E 37 to a normal or no signal position.

' Under ordinary straight or level ight the slaved relationship between the magnetic compass and the gyroscope 30 may be maintained. However, it has been found in banked turns that it is desirable to sever this slaved relationship between the magnetic compass and gyroscope and this severing is controlled by a turn indicator or rate of turn gyroscope 270. The manner in which this severence is obtained will be more fully set out in the statement of operation of the arrangement. The rate of turn gyroscope 270 -is of the type whose rotor has two angular degrees of freedom and includes a gyroscope casing 271 which supports a rotor for rotation about a horizontal axis. The casing 271 is carried by trunnions 272 in a channel shaped bracket 257. The gyroscope 270 is so arranged in the craft that upon movement of the craft about the vertical or turn axis the gyroscope will precess about the axis of trunnions 272. Spring means (not shown) serve to restore the casing 271 to its horizontal position when rotation of the craft about the vertical axis ceases. One trunion 272 carries a contact arm 273 which is betweenV spaced contacts 274, 275 and coacts therewith in a manner to become evident.

It was stated above that during manual operation of the control surfaces where heading changes are undergone the potentiometer 37 is maintained in a null or no signal condition preparatory or in anticipation of automatic pilot control being imposed.

a. switch arm 280 bears on the periphery of disc 276.

The arm 280 coacts with a fixed contact 278 in normal position of the knobv 151 when follower 277 rests in v*notch 279.

In order to avoid any inadvertent signal from the course changer 150 while the Operation Before proceeding with the statement of operation of the arrangement it may be desirable to dwell brieyon the operation of the control surface servomotors utilized in the arrangement. Such servomotors have been disclosed in the aforesaid patent to Willis H. Gille et al. and in the application of Willis H. Gille, Serial No. 447,989, now Patent No. 2,750,602. These servomotors are of such construction that the control surfaces may be manually operated without resistance thereto by the servomotor. The rudder servomotor 141, Figure 2, may be associated with its control surface upon the energization of lead wire 281 at which time such servomotor will hold the control surface in a braked condition. If either lead wires 282 or 283 are subsequently energized, the braked condition is overcome and the servomotor 141 rotates in one or the other directions depending upon which lead 282 or283 is energized. When either lead wire 282 or 283 is subsequently deenergized the braked condition is again imposed.

The operation will be considered from the time when the automatic pilot is started up and initially concerns slaving the gyroscope to the compass. This starting is initiated by closing the master switch 184. In the A. C. section controlled by pole 186 of switch 184, voltages are fed from the A. C. source through bus 188 to the potentiometer transformers, amplifiers, and gyro circuits other than lthe directional gyro rotor circuit. The directional gyroscope rotor motor is fed initially from the A. C. bus 188 through a resistor 189 to reduce the available voltage on the rotor motor and therefore to ini tially hold down its speed of rotation. The single phase winding 12 of synchro 13 is now energized and if the compass 10 and the gyroscope 30 are not aligned a v oltage will be induced in the single phase winding 18 of signal transformer 17, and this signal will be applied across the lead wires 26, 27 connected to the precession motor amplifier 20. The precession motor 28 will be operated by the amplifier 20gto apply a torque about the axis of trunnions 32 resulting in the precession of the directional gyro about the axis 34 until the single phase winding 18 of transformer 17 is positioned to a null. At this time the secondary winding 201 of transformer 199, Figure 2, which energizes the precession motor 28 through amplifier 20 additionally has its circuit completed at its lower end as shown in Figure 2 throughout contact 206 and pole 205 of relay 202, lead 297, pole 194 of relay 190, out contact 197, lead 298 to ground. Thus the full voltage of secondary winding 201 is applied to the precession motor 28 at this time.

The D. C. circuit which is controlled by pole of switch 184 is extended from battery 286 through the heating element 212 of switch 209 and thence to battery ground. After a time interval the bimetal 210 closes a circuit with Contact 211 thereby extending D. C. voltage to coil 191 by way of lead wire 284. The circuit through the coil 191 is completed to ground through the lead wire 298.

The relay now pulls in causing the relay arm 193 to engage the in contact 196 which thereby causes the A. C. source to shunt the resistor 189 thus applying full available voltage on the directional gyro rotor motor.

The closing of relay 190 causes the relay arm 194 to break the precession motor circuit between lead wire 297 and out contact 197. The precession motor circuit now extends from the relay arm 205 of relay 202 through the adjustable resistor 208 to ground. 'I'he resistor being added to the circuit of the precession motor reduces the avaiiable voltage thereof and thus reduces the torque which the motor may apply and thereby reduces the available precession rate for the directional gyro. It is presumed that the time delay and the operation of switch 209 is sullcient to bring the gyroscope in alignment with the compass and after such alignment is attained a lower rate of precession of the gyroscope is desired in order to -avoidvincreasingts sensitivity to such a point that hunting would occur during oscillations-ofthe magnetic comass.

IlWhem-theI--aireraftturns, the rate-of turn gyroscope "-270-.respondsftothis turning actionand precesses about theaxis of trunnions- 272 to close a circuit operating relay 202 -from-batteryr286, switch arm`185, lead 285, con- -tact 274 or' 275,` switch arm 273, lead 287, operating coil l=203fofrelayi202 to-.ground.l -Relay 202 pulls in and -breaks thecircuitiof the precessionmotor between out- -fcontact1206and switch orrelayarm .205. .Thus the gyro- -sflscopezmay not-ibe-iprecessed duringzturning: of the craft. lIWhen--themate ofaiturri` ofthecraftceases; .the varm 273 is Lit-automatically .-movedt to,v mid-position .between contacts 1274-and11275rto:break-the circuit through the relay coil -liazand-permit.ttheerelayarmt205 to move into engagev mmentrwithits; out-rcontact'06 1 to. permit '.the precession j .fmoton. to cfunction.

2 Iff theeaircraft is -being.,.contr.o1led..innilight, by. direct manual.- operationf-ofnthe.- control surfaces, .-thegyro stabilzedrsliders 107 and:39: of .the directional gyro rudder .'.srandbaileronapotentiometers .31; and .'36` momentarily may -fnnot .be at .'thecenters oft-their respectvemesistors 106 and 38ntherebyt-settingffup afignalaixr'theserpiclQ-bts. --Any a such existing :signahincthetrudder pickiotf 37,; Figure 2, -z s zrapplied across fthei isolatingatransformer". 266,- primary Winding:267tandthrough;transformeractionto; secondary winding 268;.1thence tb lead 290, branch dead; wire 291 to Aoutncontaotpltl .i ofnthe. rudderzngage relay. 223, relay sharm-Z226; lead Swix-@292,ftogampliierA 160,; toone; control tnelectrodegfthereof;.andefrom .fthe other grounded'fcontrol melectrode tothe .grounded -.side; of secondary winding 268. rf'fheristeeringnmotor@amplifier-1160 causes `.the-steering f. motorsf167 to-.rotatefwhichi` 'through its ,shaft- 162 rotates the drive gears 182 and 181 to position driven gears108 ..sfandAflmiihthetpicky-up37 is in theno signal position. Elus the-.picktfia maintained in a.no` signal. condition. -ho aineraiti rpaynangularly movegfabout'its roilaxis f:duringnrnanualfflcontrol1 surface operationvv causing;1 the vertical gyroscope 831`to position Athe fslidersf131 ofthe r-verticalz-gyroiruddenpotentiometenflzwand .the-slider 77 ofthe vertical, gyroiaileronf'potentiometert 76.. j The-input .circuit of-fthefrudderfampliticri 140 andthe ,input circuit t'. ofthe 4aileron amplifier, fwould. thereby become-un- .balancedresulting-nhe operation ofwthese rampliers.

Y With respect to the rudder gamplitierw140 it operates one or the other-of .its'tworelays depending .upon the -phase .--relationshiptbetween the signal. across its-.control elec- .trodes of that fromthe alternating'current source. Direct current is #fed .fromffmain lead-28tL-subleads4 293, .294 to .t amplifier 140, and, alternatively; depending .uponwhich .eratedyrelay in'arnplier 140 tollead :295, relay-arm 228,

-,out-.contactf,235, lead '340,-5throughgcentering motor"122 to-ground ori-through thefotherrelay inamplifier 140,

; lead-296relay armf229,fout contactf237lead wire 341,

e.. fthrough.. the vcenter-ing motor =122 in the opposite direc- =f-tiontofgroundfand tothe-ground ofl battery' 286. :The

n centeringwmotorlZZ through its. shaft 121, `Figure l,

.-.positionsthe slider 1120 of the trim or centering po- .v Itentiometer 118 withrespect to theresistor 119 to genl .erate a voltage between the slider 120 and thecenter tap `ofzresistorz119- which is equal and opposite to that bei 'tweenthe vertical gyro operated slider A131 and the slider fr 128-of the automatic recovery potentiometer126. Tl'iusl ...tained in atbalancedicondition by the operaticnof the centering motor Y122 whilethe control-.surfaces are .being manuallyoperated. In a similar manner, the aileron centering motor 68 maintains the input circuit of aileron amplifier 9 2 in a balanced condition while manual operation ofthc control surface is 4being exercised.

` If it be desired, automatic pilot control may be introducedby -the operation of the main engage switch 218 `whichupon--closing-completes acircuit from main lead 2288, mainengageswitch 213, out contact 25.ro.-the ':iea :lay- 246, switch arm `249'of the. relay, lead 289, operating coil 217 of the main engage relay, lead 298, switcharm 280, contact 278 to ground, and to the ground ofbattery 286. When coil.217 is energized the main engage relay 216 pulls in and completes a circuit from lead 289, lbranch lead 299, arm 219 of relay 216, in contact 221, lead 300, operating coil 224 of the rudder engage relay 144, to ground and to the ground of battery 286.

As the rudder Aengage relay 144 pulls in the association between the. isolating transformer secondary 268 :and the steeringmotor amplifier 160 is broken between .the relay arm 226 and the out contact .231 thus the-directional gyrovrudder'pick-'oi 37 isv no longer maintained v in a null condition. The steering, motor amplifier` 160 is now associated. throughthe arm'226, in contact..232,11lead 157 with .the .course.-.change potentiometer 7154. The

v -servomotorbrake .lead;:281 is associated through the in contactx234, arrn227-,flead .300, with the D. C. energized -Ylead.293 thusscausingFthe rudder control surface-to'be uplacedin alocked or -braked-condition by the( servois=now associated-through arm 228, in contact 236,- lwith noneclutch lead-"283. ofservomotor 141 and theother am- .plitierrelaysloutputnleadr296 istassociated through arm :1229,- in.contactr238:-witl1l;the other-clutch lead. 282. 0f

y.servomotor 141.

1 In a similar manner,tthe operation of the main engage A:relay 216.in causing farm.220 to engage the incontact 3Qi222-f operates@ the iaileron. engage relay.(notl shown). to

thus cause the aileron servomotor 96 to assume arbraked conditionfwith respect tothe -aileron lcontrol surfaces and toassociateftheaileron amplifier relay output leads :with

y-the;.aileronrservomotor The aircraft is now,- underautomatic.pilot-'control If such control: be. fintroduced when. the 'aircraft is.. in agdesircd. :direction- 'of.vv headingtsuch'. heading Awillvberrnaint ..tained f Ifftthe craft deviatest from-such: heading-,athen dis vrectional gyro. rudder potentiometer resistorilfzandathe 40, directionaltgyro aileron potentiometer resistorssfwould .1 be. rotated -or -carriedby vthe -craftfwithfrespect tortheir gyro stabilized-.sliders .1107 andf-39. resulting in a-signal .being generated or .derived from,thelpickgoffs-r-37sandr36.

y Tl1e.rudder ampliierf140 andthe aileron-amplifiers in D response to `these signals causedby.dev.iation of-thefcraft willoperate the lrudder servomotor141;.and ;the:aileron 1servomotor -96 resulting' in a.=bankand ;turning ofpthe craft toward the desired heading. The aileron andru'dder -serv0motorsfalso position their respective sliders'47 and o 2118 to rebalanceeach network. ln response to vthebanking and turning of the craft, the vertical -gyro Yadjustsi the sliders 131 :and 77 of potentiometers-129 and76 lputting in a reversezsignal in the aileron and rudder bridge-netr. worksfrom that resulting from the initial deviation of .the craft. in response tothereverse-signal, from the`operation of. theyertiCal-gym, the control surfaces,-namely the rudder-andailer-on, move; back to their normal-positionn As 1the,craft-. approaches its desired heading', the G0 -signal from the -piclcoffs-36and 37 decreases resulting in an unbalance in the aileron and rudder bridge networks.

There isthus aturtherpreponderant reverse signal inthe aileron and fbriidgefnetworks respectively which cause.` the '.servomotorspfor ha-fnuddenand aileron to move. their rcontrol surfacesirt.an;.opposite direction1--from-.that in .which they were moved .following the initial deviation.

In response. to,..this..oppositepositioning of; the-com vtrol surfaces, webstek offfthefaircraft decreases and sliders 131A and v77-v are movedfback `toward their normalpositions by. gyrof83...! This-adjustment of the-verticaL-fgyro sliders vlland.7.7..again.causes the movement of -thecontrol surfaces baclc toward. normal. When 4the craft reaches itsdesired heading, the control sur-faces areagain in the same position as whenthe craft initiallyfdeviated.

If changes in heading of the aircraftthrough the auto- 75 matic pact control be desired, the knob 151 is rotated in the direction depending upon which direction the heading-is to be altered. The knob 151 when displaced moves the slider 153 of potentiometer 154 with respect to its resistor 155 to generate a signal which is applied from Slider 153, lead wire 157, in contact 232, relay arm 226, lead 292, to a control electrode of the steering motor amplifier 160. The other portion of the control circuit of amplifier 160 extends from the grounded electrode of amplifier 160 to the ground lead 156 of potentiometer 154. The steering motor 167, as controlled by the ampliiier 160, through its drive gears 181 and 182 drives the gears 40 and 108 which support the potentiometer resistors 38 and 106.

The steering motor 167 also drives the rotor 177 of the velocity signal generator 174. The steering motor requires a minimum signal on the amplifier in order to obtain sutiicient torque to overcome friction in the parts driven by the motor. The excess of the signal from potentiometer 154 over that minimum signal permits the velocity of the steering motor to increase. The increase in the velocity of steering motor is retiected in an increase velocity signal in the winding 176 of velocity generator 174. The speed of the steering motor is permitted to increase until the velocity signal generator winding 176 has induced therein a signal equal to the excess of the potentiometer signal over the minimum signal required to drive the steering motor. The rate at which the steering motor rotates therefore depends upon the amount of signal obtained from the potentiometer 154 and it is thus seen that the steering motor may be operated at selective variable rates.

As the steering motor through its driving gears 181 and 182 drives the resistors of potentiometers 36 and 37 there is a relative displacement of these resistors with respect to their sliders 39 and 107. A signal is thereby generated in the pick-ups 36 and 37 which is applied respectively to the aileron and rudder bridge networks to unbalance the same. The aileron and rudder amplifiers operate their control surfaces through their servomotors and the plane is thereby placed in a banked turn. In response to this bank of the craft the vertical gyro operates the sliders 131 and 77 to introduce a signal in the rudder and aileron bridges which tends to move the control surfaces back toward normal position. At this time the rudder and aileron bridge networks-are balanced by the vertical gyro signals from potentiometers 76 and 129 offsetting the directional gyro signals or course change signals from potentiometers 36 and 37.

When it is no longer desired to continue in the banked turn the knob 151 is moved back to a normal position returning the slider 153 to the center tap of resistor 155. The steering motor 167 no longer rotates and the resistors 38 and 106 may be said to be relatively fixed to the craft at this time. As the craft in its banked attitude continues to turn, the resistors 38 and 106 move under their sliders 39 and 107 to reduce the signal from the pick-ups 36 and 37 in the aileron and rudder bridges. There is now a preponderance of vertical gyro signal which results in the opposite positioning of the ailerons and rudder thereby decreasing the banked attitude of the craft. This decrease in the banked attitude results in the reverse movement of slider 77 and 131 by the vertical gyro 83 with the control surfaces consequently being moved back toward their normal position. The action is continuous in that as the signals from the directional gyro rudder and aileron potentiometers 37 and 36 decrease an opposite control surface displacement is applied to the rudder and ailerons from that initially given to go into the bank turn. The resulting lessening in the amount of the bank is felt by the vertical gyro which unbalances the aileron and rudder amplifier networks to cause the control surfaces to be moved back toward normal. When the directional gyro rudder and aileron signals are removed, the craft attains the attitude previously had when 12 course change was initiated. The craft is now stabilized on the new heading attained.

The operation of the automatic recovery feature will now be considered. It was previously stated, that while the aircraft control surfaces were being manually operated while in ight that the centering motors 122 and 68 for the rudder and aileron bridges were controlled bythe respective amplifiers 140 and 92 to maintain the rudder and aileron amplifier bridge networks in a balanced condition despite changes in attitude of the craft. Thus the automatic pilot might be engaged with the control surfaces while the craft is in other than normal level ight attitude. Since the automatic pilot may be engaged in other than normal level ight attitudes of the craft, it appears desirable to provide some means for automatically returning the craft to normal flight attitude upon the automatic pilot taking control. This feature is especially desirable during emergencies. For this purpose the rudder bridge is provided with an automatic recovery potentiometer 126 and the aileron bridge is provided with an automatic recovery potentiometer 73. If the effect of the centering or trim potentiometer 118 be removed in the rudder bridge network, itis apparent that during manual operation the control voltage is dependent upon the relative positions of the sliders 131 and 128. Similarly in the aileron network with the eect of the trim potentiometer 57 removed any unbalance voltage in the aileron bridge network upon change in attitude of the craft depends upon the relative displacement of the sliders 77, and 74 if the craft changes attitude while being manually controlled. In this consideration, the effects of the servo balance potentiometers 113 and 46 is omitted for simplification since these control surfaces may be assumed to be in normal position and the sliders and 47 will also be in normal position on their resistors.

With the aircraft in a banked attitude therefore, and with the potentiometers 118 and 57 effectively removed the base point of the bridge networks becomes the potentiometer slider 128 in the rudder bridge network and the slider 74 in the aileron bridge network. The means for removing the e'ect of the potentiometer 118 and 57 is shown in Figure 2. When it is desired that the aircraft be returned to a level or normal flight attitude, the automatic recovery switch 241 is operated to extend a circuit from energized lead 288, lead 308, switch arm 242, through the operating coil 247 of the automatic recovery relay 246 to ground. This relay 246 pulls in and D. C. voltages are extended from lead 288, lead 309, in contact 254, relay arm 249, lead 289, through the main engage relay operatingrcoil 217. The operation of the main engage relay results in the subsequent operation of the rudder and aileron engage relays and their locking themselves in as described. D. C. is also extended from lead 288, lead 293, branch lead 310, relay arm 251, in contact 252, lead 311, through the coil 259 of the locking relay 258 to ground. The relay 258 establishes its own holding circuit from lead 288, lead 312, switch arm 262, in contact 265, coil 259 to ground, and the grounded lead of battery 286.

When relay 258 operates, it opens a circuit for the primary winding 64 of transformer 61 between switch arm 261 and out contact 263 connected to the alternating current source and grounds the primary winding 64 through relay arm 261 and in contact 264 which is connected to ground. The secondary windings 60 and 63 of transformer 61 are no longer energized and thus the centering potentiometers 118 and 57 are rendered inetfec tive. lf the craft be in a banked attitude, a signal wif be generated between slider 131 and slider 128 in the rudder bridge network and slider 77 and slider 74 in the aileron bridge network resulting in the return of the craft to an attitude depending upon the adjustment of the automatic recovery sliders 128 and 74. While the operation of the auto recovery switch 241 and the subsequen' operation of the relay 246 associates the isolating trans 2113 former 266 of Vthe directional 'gyrorudder .potentiometer 37 with the steering motor amplifier i160 bymeans of lead 290, switch contactf256, switch arm'250, lead 292 yet since the pick-olf 37 is being-maintained ina no signal position during manual control'of the rudder and -ailerons there is no signal output 4from the'pick-otf 37 causing additional operation of the steering motor amplifier 160. After the 6 or 7 second period of delay by dash pot 244 the auto recovery switch 241 is automatically'opened, and the pick-'off 37 is-isolated from the steering motor amplifier 160 at out contact 231 inthe rudder engage relay and at in contact 256 in the auto recovery relay 246 consequently stabilized directional control will be thereafter imposed.

In some instances, it maybe .desired while in a turn resulting from the displacement of the manually operable slider 153 of potentiometer l154 to utilize the automatic recovery feature. It has been shown'that during such manually initiated turns the slider 107 of directional gyroscope potentiometer'108 is displaced with respect to the normal point of resistor .106 .and that the normal point of resistor 106 is brought under the slider 107 by the movement of the craft to place pick-olf 37 in no signal position even though the control knob 151 may have been placed in normal position. It may be desirable-to'avoid this movement of the craft required to balance or adjust the pick-otf'37 to no signal position and in such instance the auto recovery switch 241 initiates' this operation. If the craft is in a turn initiated by the`movement of knob 151 as stated, the rudder input. circuit of amplitier'140 is balanced by the relative displacements of the slidersy 131 and 107 withrespect to their vresistors 130 and'106. Similarly the aileron amplifierinput' circuit is4 balanced by the relative displacement of slider 77 and with'respect to its resistor 78 to Aoffset the displacement of slider 39 with respect to its resistor 38.` 'The' operation `of theY auto recovery switch 241 results in the energization of operating coil 247 of relay 246. 'Iheoperation of'the'relay'246 results in the operation f locking lrelay-258 `with the consequent grounding ofthe secondary winding-64 of transformer 61. The grounding of this primary-Winding 64 renders ineffective the turn-potentiometer 154l and the rudder and aileron centering potentiometers 118 and 57. The relay 246 through the arm 250 and in contact 256 associates the isolating transformer 266 of pick-off 37 with the steering motor amplifier 160. The steering motor 167 is operated by the amplifier 160 due to the signal from pick-off 37 and moves this rudder pick-off and aileron pick-off 36 to no signal position.

The vertical gyro 83 has operated sliders 131 and 77 in the rudder and aileron networks. 'Ihe position of slider 131 with respect to auto recovery potentiometer slider 12S and thek position of slider 77 with respect to slider 74 determine the unbalance of the rudder and aileron bridge networks. The aircraft therefore has its rudder and ailerons moved from normal position to remove the bank attitude of the craft and to return it to an attitude which has been preselected by the positioning of sliders 128 and 74. After the brief interval of time the auto recovery switch 241 is automatically opened and directional control from the directional gyro pick-off 37 is again established since the steering motor amplifier 160 has now been isolated from this pick-off. The aircraft has thus been permitted to regain a preselected attitude on a stabilized heading without the aircraft being required to turn through an angle necessary to wipe out the signal in the directional gyro rudder potentiometer 37.

It will now be appreciated that there has been provided a novel automatic pilot for an aircraft using as a control element a slaved directional gyro which is provided with an arrangement for rapidly aligning it with a compass and to provide slow precession of the gyroscope after the aligned condition is attained. Further novel combinations of relays and interlocks associated 14 witht gyroscope -for controlling an aircraft have been described.

While many 'of the signal pick-offsv andiother features have been: illustrated by `electrical constructions it is'believed obvious that thebroadaspects of-ths'inventicnare applicable to"otl1er,typesA of autornaticipilots other-than that. selected for"il'lustrating"the invention. Therefore since many' changes-"could'bemade inthe above-constructionand'manyditferent embodiments of the-invention could be madewithoutdeparting' from the scope '.thereof, it is tofbe"understood'that allmatter contained -in-the above 'description-and= illustrated in the accompanying drawing shall'A be "interpreted4 as illustrative only a'nd`sn0t as an'intentionN to limit the invention to the 15 specific form-disclosed.

IA claim as'my-invention:

1. Controlapparatu'sofor aedirigiblecraft having a `control surface and ypower means'normally inoperatively related thereto, said apparatus'comprising: a magnetic compass, a directional gyroscope'having an electrically driven `rotor, electrical' torque; applying -meansfor pre- Ncessing4 said j--gyroscopef-means-responsive solely to misfalignment ofsaidcompass-and-gyroscope for controlling ""'said torque emeaus, ajsigr'ial generating means-consisting "of-'two relativelyadjustable coacting-parts, one-part- -being l"adjustei'l''byvsaid lcraft,'the -other-f -partl being adjusted by saidgyroscope, means lifor foperatively vassociating said power means with said control surface andcontrolling -'sa.id\-powenimeansfromrsaidl-signalrgenerating means on mis'alignmenti 'off saidfl craft'andfgyroseope 'r while -controlling Ysaid-torque-means lby saidmeans responsive-.to mis- '-alignment-f'of is'aidcompassand-:gyroscopev and motor l' -rneansf controlled-:by: saidasignalhgenerating 'means while `astrid-powermeans islinoperatively related'to said: control surface for readjusting the relative position ofsaid-gyro- --scopezand-teraft'iadjustedi parts so that` said= generating t' means is in aine'. signal condition when the power. means is; subsequently 'f operatively Vassociated with, .said control fsurface;`1electric"circuit vmeans-f-for energizing said gyro- 40s-'scope rotor-:and: said gyroscope-torque applying means includingmeans for .momentarily initially decreasing the ivoltager applied to said rotor :driving means while increas- :ing the 4voltagevapplied to said A,torque applying means to 4more quickly align the gyroscope and compass. 2. lControl apparatus for an aircraft comprising: signal providing means including a potentiometer having a slider and a resistor part for producing an alternating voltage of; varying magnitude and-reversible phase; a gyroscope responsive to change in craft heading; means for stabilizing one potentiometer part by said gyroscope, said other 4part :being carried by said craft; reversible electric power ymeans operatively-associable with a control surface of said craft and normally controlled by said potentiometer means; motor Ameans for positioning said other potentiometer part'with respect to said craft; selective manual means for associating said power means and said control surface:means for: controlling said motor means from said potentiometer -means while said power means is operativelyf disassociated from said control surface; manually operable means for controlling said motor means while said power `means is associated with said control surface to"=elect change in craft heading; and means for initially preventing 'the operativeassociation of said power means with said control surface by said selective manual means if said manually .operable means is displaced from .amormal unoperated position.

3. Control apparatus for an aircraft comprising: control signal providing means including a potentiometer having a'sliger and a resistor part for producing on relative displacement of the slider and resistor midpoint an alternating voltage of varying magnitude and reversible phase; a-gyroscope responsive to change in craft heading; means' for Astabilizing one potentiometer part by :said

=-gyroscope, said other part being carried by said craft;

76 f reversible electric power meansassociable-.witha control surface of said craft and normally controlled by said potentiometer means; motor means for positioning said other potentiometer part with respect to said craft; means for controlling said motor means from said potentiometer means while said power means is operatively disassociated from said control surface to align the slider and resistor midpoint; manually operable means for controlling said motor means while said power means is operatively associated with said control surface; a pair of alternative manually operable switch means for associating said power means with said control surface; and means responsive to operation of one switch means for rendering ineffective the manually operable means.

4. Control apparatus for an aircraft comprising: a power means for controlling said craft about its roll axis; a power means for controlling said craft about its vertical axis; a separate balanceable control system, including a gyroscope operated pick-off, for controlling each power means each pick-off being connected to the same axis of a gyroscope; motor means operatively coupled with both said gyroscope pick-offs; operable switch means for simultaneously disconnecting each said power means from its balanceable control system; and further means connecting a gyroscope piclrot to said motor means for control thereof during the disconnection of the power means to thereby adjust said pick-offs into no signal producing positions to thus align said pick-ois with said gyroscope.

5. The apparatus of claim 4, with a manually operated pick-olf for controlling said motor means to provide for operation of both pick-offs and power means to cause banked turns of said craft resulting in changes in position of said craft about said vertical axis, when said balanceable systems are connected to both said power means.

6. Control apparatus for an aircraft having ailerons and rudder control surfaces which may be manually or automatically operated, said apparatus comprising: power means operatively associable with said ailerons; power means operatively associable with said rudder; a vertical gyroscope; a directional gyroscope; a balanceable control means for said aileron power means; a balanceable control means for said rudder power means; each control means including a power means operatedpick-otf, a craft trim pick-off, a vertical gyro pick-off, and a direction gyro pick-olf; motor means drivingly associated with said directional gyro pick-off, means responsive to the unbalance of a control means during manual operation of said surfaces while said corresponding power means is disassociated from its control surface for operating the trim pickot for. rebalancing said control means during changes in craft attitude, and selective manually operable switch means having a delayed release for controlling said motor means momentarily from a said directional gyro pick-off to thereby place said directional gyro pick-off in a normal position, associate both power means with their respective control surfaces and render said trim pick-offs ineffective, to thereby cause said craft to follow the position of the gyroscope pick-offs in the rudder and aileron axes of said craft.

7. In control apparatus for an aircraft in combination: a magnetic compass, a directional gyroscope, precessing means for aligning said compass and gyroscope; a craft heading control pick-ot operated upon relative heading movement of said gyroscope and craft; a motor means to drive said pick-olf for removing said relative movement, differential means including a second and third pick-off respectively controlled by said compass and gyroscope for operating said precessing means, means for controlling the attitude of said craft from said pick-olf while said diterential means operates said precessing means; and switch means for initially additionally automatically connecting said craft control pick-olf with said motor means for control of said motor an interval after said differential means operates said precessing means to reduce the necessary operation of said motor means to place said craft pick-off in no signal position.

8. In control apparatus for an aircraft in combination: 'a magnetic compass, a directional gyroscope, precessing means for aligning said compass and gyroscope; a craft heading control pick-off operated upon relative heading movement of said gyroscope and craft; a motor means to drive said pick-olf for removing said relative movement, differential means comprising a synchro transmitter and transformer each having a winding tixed to the craft and each having a movable winding one movable winding being positioned by the compass and the other by the gyroscope and responsive to the difference of their positions for operating said precessing means, switch means for automatically connecting said heading control pick-olf with said motor means for control of said motor an interval after said differential means operates said precessing means to reduce the necessary operation of said motor means to remove said relative movement; power means for controlling the attitude of said craft about an axis, and selective means for controlling said power means instead of said motor means by said pickoti' after said interval.

9. In control apparatus for an aircraft in combination: a magnetic compass, a directional gyroscope, a pair of interconnected synchro generator and control transformer windings fixed to the craft each with a related movable winding, one movable winding positioned by the compass the other by the gyroscope, precessing means connected to the movable transformer winding and controlled therefrom for aligning said compass and gyroscope; a craft heading control pick-off operated upon relative heading movement of said gyroscope and craft; a motor means to drive said pick-olf for removing said relative movement, differential means controlled solely by relative displacements of said compass and gyroscope for operating said precessing means, 'and switch vmeans for automatically connecting said heading control pick-off with said motor means for control of said motor an interval after said diterential means operates said precessing means to reduce the necessary operation of said motor means; ad means for controlling the relative available lprecessing effect of said precessing means whereby it is increased during said interval but decreased thereafter.

10. In control apparatus for an aircraft in combination: a magnetic compass, a directional gyroscope, preceasing means for aligning said compass and gyroscopes; a craft heading control pick-ofi operated upon relative heading movement of said gyroscope and craft; a motor` means to drive said pick-ofi for removing said relative movement, differential means having movable elements controlled solely by said compass and gyroscope for operating said precessing means, switch means for automatically connecting said heading control pick-off with said motor means for control of said motor an interval after said differential means operates said precessing means to reduce the necessary operation of said motor means; power means for controlling the attitude of said craft about an axis, selective means for controlling said power means instead of said motor means by said pickoff after said interval; a manually operable pick-olf for controlling said motor means while said gyroscope-heading control pick-off controls said power means, to change the heading of said craft; and means responsive during change of heading of said craft to render said precessing means ineffective.

ll. In control apparatus for an aircraft in combina tion: a magnetic compass; a directional gyroscope; preees sing-means on said gyroscope for aligning said compase andegyroseope; a craft heading control pick-oli having two relatively movable parts and connected to be operated upon relative movement of said gyroscope and craft; g motor means adapted to drive one part of said pick-off for removing said relative movement; differential means hav ing. movable elementscontro'lled solely. by` said compass and gyroscope and connected for operating said precessingmeans; switch means for automatically connecting sadheading pick-olf with said motor means for control of said motor an interval after said differential means operates said precessing means, to reduce the necessary operation of said motor means; power means for controlling theattitude of said craft about an axis; manually opera# ltive selective means for effecting the control of said powermeans instead of said motoi means by said pickoff after said interval; anda manually operable pick-oft' for controlling said motor means while said heading control pick-off controls said power means, to change the heading of said craft; and means to prevent saidselective means from being effective initially until said manually operable pick-otf is in a normal unoperated position.

l2. Control apparatus for a dirigible craftcomprising; a compass responsive to the earths magnetic lield; 'a directional gyroscope hayingan electrically driven rotor; means for aligning said gy ro S }9psY with4 said compass, said aligning means including an electrical torque means for processing said gyroscope about its, vertical. axis; matinsI for connecting said torque applying means to a power source including alternative. circuits one having less` resistance than the other and time delay controlled means; said time delay means being effective to. com.- pletesaid one circuit to momentarily increase the voltage applied to said torque applying means.I and thereafter opening said one circuit to decrease. the voltage. applied to said torque applying means; and switch meansfor energizing said rotor and time delay means.

131. Control apparatus for an aircraft comprising: a directional gyroscope; a magnetic compass; preces'sing means on said gyroscope for aligning said compassand gyroscope; a control signal pickfotf operated upon relative heading movement of said gyroscope and craft; a mptor means vfor removing the effectof said-movement; differential means having relatively movable elements solely controlled by said compass and gyroscope for supplying control signals when the compass and gyroscope are misaligned; means for connecting said precessing means with said differential means for response thereof to said control signals; power means for controlling the craft heading; switch means; manually operable selective means for operating said switch means for alternatively controlling said power means or said motor means from said gyro scope-craft pick-off; a manually operable pick-off for controlling said motor means while said gyroscope-craft pickoff controls said power means, to change the heading of said craft; and interlock means to prevent operation of said switch means by said selective means until said manually operable pick-off has been initially placed in a normal position` 14. Control apparatus for a dirigible craft comprising: a compass responsive to the earths magnetic eld; a directional gyroscope having an electrically driven rotor; means for aligning said gyroscope with said compass, said aligning means including an electrical torque means on a horizontal axis of said gyroscope for precessing said gyroscope; means for connecting the rotor driving means and torque applying means to a power source; manually operable means for controlling said connections and time delay means responsive to operation of said manual means and connected to energizing circuits for the rotor and torque means and effective to subsequently increase the available voltage applied to said rotor driving means and to subsequently decrease the available voltage applied to said torque applying means.

15. In control apparatus for a dirigible craft; a direction sensitive instrument; a gyroscope having an electrically driven rotor included in a circuit; electrical torque applying means supported on a horizontal axis of said g roscope for precessing said gyroscope included in a circuit; a thermal actuated device having an energizing circuit, means responsive to misalignment of said sensitive instrument and-said gyroscope for controlling said-torqule'! applying means circuit; and manually operable meansVt-'Lor energizing saidl circuits, saidrotor and' torque applying means circuits being additionally controlled by said ther| mal devicefor initially momentarily simultaneously ining momentarily the resistance of said torque applyingl having a slow release foi'. inter-connecting said pick-olf' and motor means whenin the operated position for coni trollingsaid motormeans from said'pick-oif momentarily to null.` said pick-othand further switch means including' circuit maintaining means controlled initially by said' selective switchmeans during-movement to the operated position for controlling the` operative relation of staid power means and-saidsurface.

17. A manual-controller forA an` aircraftautomatic pilotadaptedfor connection to` and for disconnection from the "control surfaces of the craft; comprising a turn knob'v having an. operative and an inoperative position, switch meansoperatively-connected:to s'aid turn knob and activi'-` ated.- to an open'circuit condition when the turn knobisin its operativeposition and to a closed-'c ircuitlcon-y dition` when theturn knob isin its inoperative psition', other. switch. means interconnected4 with vsaidfirst siii/itchv meansand operatively connectedwith saidfautoma'tic pilot andadapted for engaging-said-pilotL with said'controh surfaces onlyfwhen said= knob is il'its inoperative posi-" tion, and a relay connected with both of said switch means and energized when the pilot is engaged with said control surfaces for maintaining such engagement notwithstanding subsequent operation of the turn knob to its operative position.

18. A manual controller for an aircraft automatic pilot adapted for connection to and for disconnection from the control surfaces of the craft, comprising a turn knob having an operative and an inoperative position, switch means operatively connected to said turn knob and actuated to an open circuit condition when the turn knob is in its operative position and to a closed circuit condition when the turn knob is in its inoperative position, other switch means interconnected with said rst switch means and operatively connected with said automatic pilot and adapted for engaging said pilot with said control surfaces only when said knob is in its inoperative position, a relay connected with both of said switch means and energized when the pilot is engaged with said control surfaces for maintaining such engagement notwithstanding subsequent operation of the turn knob to its operative position, and holding means connected to said second switch means and energized by the operation of the second switch means for maintaining the relay energized.

19. A manual controller for an aircraft automatic pilot adapted for connection to and for disconnection from the control surfaces of the craft, comprising a turn knob having an operative and an inoperative position, switch means operatively connected to said turn knob and actuated to an open circuit condition when the turn knob is in its operative position and to a closed circuit condition when th e turn knob is in its inoperative position, other switch means having an oi and an on position interconnected with said first switch means, a selector knob operatively connected to said other switch means for operating said other switch means, and said other switch including means operated by actuation of said selector knob from off to on position for connecting said operatively associated with the.y

19 pilot with a source o f current for energizing the electrical components thereof.

20. A manual controller for an aircraft automatic pilot adapted for operative connection to and for operative disconnection from the control surfaces of the craft, oomprising a turn knob having an operative and inoperative position, switch means operatively connected to said turn.

knob and actuated to an open circuit condition when the turn knob is in its operative position and to a closed circuit condition when the turn knob is in its inoperative position, other switch means interconnected with said iirst switch means and operatively connected with said automatic pilot and adapted for operatively engaging said pilot with said control surfaces only when said knob is in itsinoperative position, and a relay connected with both ofsaid switch means and energized when the pilot is operatively engaged with said control surfaces for maintaining such engagement notwithstanding subsequent operation of the turn knob to its operative position.

21. A manual controller for an aircraft automatic pilot adapted for operative connection to and for operative disconnection from the control surfaces of the craft, comprisinga turn knob having an operative and an inoperative position, switch means operativelyl connected to said turn knob and actuated to an open circuit condition when the turn knob is in its operative position and to a closed circuit condition when the turn knob is in its inoperative position, other switch means interconnected with said first switch means and operatively connected with said automatic pilot and adapted for operatively engaging said pilot with said control surfaces only when said knob is in its inoperative position, a relay connected with.both of said switch means and energized .when the pilot is operatively engaged with said control surfaces for main-v taining such engagement notwithstanding subsequent operation of the turn knob to its operative position, and holding means connected to said second switch means and energized by-the operation of the second switch means for maintaining the relay energized.

22. A manual controller for an aircraft automatic pilot adapted for operative connection to and for operativedisconnection from the control surfaces of the craft, comprising a turn knob having an operative and an inoperative position, switch means operatively connected to said turn knob and actuated to an open circuit condition when the turn knob is in its operative position and to a closed circuit condition when the turn knob is in its inoperative position, other switch means having an olfand an on position interconnected with said iirst switch means, a selector knob operatively connected to said other switch means for operating said other switch means, and said other switch including means operated by actuation of said selector knob from an off to an on position for connecting said pilot with a source of current for energizing the electrical components thereof.

References C ited in the tile of this patent UNITED STATES PATENTS 1,982,702 Sperry Dec. 4, 1934 2,126,855 Wunsch et al Aug. 16, 1938 2,140,191 Schuchardt et al Dec. 13, 1938 2,357,319 Esval et al Sept. 5, 1944 2,415,429 Kellogg et al Feb. 11, 1947 2,429,642 Newton Oct. 28, 1947 2,466,702 Hamby Apr. 12, 1949 2,499,664 Meredith Mar. 7, 1950 v2,524,756 Braddon et al Oct. 10, 1950 2,539,411 Esval et al. Ian. 30, 1951 2,539,482 Rothschild Jan. 30, 1951 2,570,905 Young et al. Oct. 9, 1951 2,589,834 MacCallum Mar. 18, 1952 FOREIGN PATENTS 871,085 France Ian. 3, 1942 U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,816,722 December 17,1957

John W. Anderson It is hereby certified that error appears in the printed spe ficatign of the abo've numbered patent requiring correction and that the 8a' Letters Patent should read as -corrected below.

Signed and sealed this 4th day of March 1958.

(SEAL) Ateet:

KARL H. MEINE ROBERT C. TSON Attestng Officer Comnssioner oPatents U. S. DEPARTMENT 0F COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,816,722 December 17,1957

John W. Anderson It is hereby certified that error appears in the printed spe of the abo've numbered patent requiring correction and that the sa' Patent should read as corrected below.

. lfcaton g Letters Column 14, line '75, after "means" insert '*operatJJrely--.4

Signed and sealed this 4th day of March 1958.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. ATSON Attestng Officer Commissioner oPatents 

